CVE-2026-64586

In the Linux kernel, the following vulnerability has been resolved:

wifi: brcmfmac: drain bus_reset work on device removal

brcmf_fw_crashed() and the debugfs "reset" entry both schedule

drvr->bus_reset, whose callback recovers drvr through container_of()

and dereferences it. The removal path frees drvr (brcmf_free ->

wiphy_free) without draining the work, so a bus_reset callback pending

or running during removal can outlive drvr.

Cancellation cannot live in brcmf_detach() or brcmf_free(): the work

callback reaches teardown through the bus .reset op (PCIe

brcmf_pcie_reset -> brcmf_detach; SDIO brcmf_sdio_bus_reset ->

brcmf_sdiod_remove -> brcmf_free), so cancelling there would wait for

the running work and deadlock.

Add a per-bus mutex (bus_reset_lock) and route all arming through

brcmf_bus_schedule_reset(), which under the lock skips when the bus is

marked removing. Each bus remove entry calls

brcmf_bus_cancel_reset_work(), which under the same lock sets removing

and cancels the work. Holding the mutex across cancel_work_sync() makes

the set-removing + drain step atomic. Every producer reaches the arming

path from process context -- the PCIe firmware-halt notification runs in

the threaded IRQ handler (brcmf_pcie_isr_thread) and the SDIO hostmail

path runs from the data workqueue -- so the mutex is taken only in

sleepable contexts. Where applicable the remove entry first stops the

firmware-crash producer: on PCIe mask the mailbox and synchronize_irq;

on SDIO unregister the bus interrupt and cancel the data worker, which

also reports firmware halts through brcmf_fw_crashed(). The mutex is

initialized at bus allocation. The SDIO suspend power-off path frees

drvr through the same brcmf_sdiod_remove() and takes the same lock;

resume re-allows the work only on a successful re-probe.

Also guard brcmf_fw_crashed() against a NULL bus_if/drvr: it can fire

before brcmf_attach() wires up drvr, and it dereferences drvr

(bphy_err/brcmf_dev_coredump) before reaching the arming gate.

The bus_reset work is shared across buses, so the drain is applied to

every remove path: PCIe (the .reset op introduced by the Fixes commit),

SDIO (arms the same work through brcmf_fw_crashed()), and USB (via the

debugfs "reset" entry). cancel_work_sync() drains a running or pending

bus_reset work item before removal frees drvr, and patch 1/2 makes the

scratch-buffer release safe when reset teardown has already released

those DMA buffers.

This patch fixes the lifetime of the bus_reset work item itself. It does

not attempt to address the separate, pre-existing lifetime of the

asynchronous firmware completion started by the PCIe reset path. That

callback needs its own lifetime/ownership protocol and is being tracked

separately.

This issue was found by an in-house static analysis tool.